#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

int main() {
	int arr[9] = { 1,2,3,4,5,1,2,3,4 };
	int ret = 0;
	for (int i = 0; i < 9; i++) {
		ret ^= arr[i];
	}
	printf("%d", ret);
	return 0;
}
